196 TRANSACTIONS OF THE [aPR. 16, 
Comparisons. Typically this rock is a tonalite or very 
quartzose hornblende biotite diorite, and in chemical composites 
is very like the original tonalite described by Vom Rath.* 
Structurally there is no special likeness. Both chemically and 
structurally it resembles an intrusive mass described by Dakyns 
and Teall from near Loch Lomond, Scotland.t+ This is of very 
similar composition, and differentiated in the same way as the 
St. John rocks, but to a much greater extent. Porphyritic 
orthoclases appear only in the most acid varieties, and are not 
usually zonal. They seem to be intermediate in size and 
character between the small zonal crystals which one may 
ascribe to cooling from fusion in which water is subordinate, 
and the enormous twinned non-zonal orthoclases, usually grano- 
phyric in structure, such as those lately described by Dr. Lawson 
from California granites.{ The latter variety is perhaps allied 
to the feldspars of the pegmatite veins, as being due to the 
presence of a large amount of water in the magma. 
AGE OF THE INTRUSION.—The resemblance of parts of the St. 
John granitic areas to the great belts of Devonian granites 
stretching across central New Brunswick, is noted in the. Survey 
Report for 1871. Whether this comparison holds good also with 
regard to microscopic peculiarities, | do not know, as I have not 
seen any sections or microscopic descriptions of Devonian gran- 
ites. It is not at all impossible that the intrusive granites of the 
southern hills may prove to be of this age; but their relations 
to the Cambrian slates seem to be against this view. They are 
certainly post-Laurentian, for as already described, they break 
through the limestones, altering them along the contact. They 
are as certainly pre- Carboniferous, for they are unconformably 
overlain by flat lying Lower Carboniferous conglomerates. The 
relations to the Cambrian slates are doubtful, the only contacts 
being on Kennebecasis Bay, one a little northeast of Drury’s 
Cove; the other at Sandy Point, to the southwest of it, and 
both these are faulted. Unless these faults are heavy, the 
granite would appear to be pre-Cambrian, for not the slightest 
evidence of contact alteration can be seen, even in the seams of 
fossiliferons limestone. But it must be admitted that there is 
no evidence of the extent of the fault, and that the granite diorite 
has not had a great influence on the earlier Laurentian lime- 
stone. No Cambrian conglomerates are exposed here. The 
relative abundance of diabase dykes in the granite and in the 
* Zeit. d. d. geolog. Gesell, 1864, X VI., p. 249. 
+‘ Plutonic rocks of Garabal Hilland Meall Breac.” Quart. Jour. Geol. Soc: 
XLVIIL., p, 104, May, 1892. 
{ ‘‘Geology of Carmelo Bay.’”’ Geol. Dep. Univ. of Cal., Bull. No.1. 
